Is most of a vegetable’s good in its skin?
The good here being a catch-all term that covers any number of vitamins, minerals and other nutrients. The whole-food crowd would have you believe that if you — gasp — peel your vegetables and only eat the insides then you’re missing out on the best bits. The truth isn’t so clear cut. The skin usually is chock full of goodness, but so is the flesh, and a lot hangs on what else happens between the peeling and your stomach.
There are many different kinds of vegetables and fruit which makes generalisations a little hazardous. This is New Zealand, though, where we throw ourselves of bridges for fun, so let me plough on regardless.
The skin of many fruits and vegetables does contain a higher proportion of nutrients compared to the flesh beneath. That’s not quite the same as saying that the skin contains more good than the flesh which suggests that, once peeled, the remains are just empty calories with nothing but an illusion of nutrition about them. That’s not how it works.
The skin is a very valuable source of all kinds of goodies, from fibre to vitamins and minerals — but so is the flesh. Skin a tomato and you remove perhaps a quarter of its vitamin C. That is a lot, but it still clings valiantly on to three quarters of its nutritional value.
Even though it is false — strictly speaking — the claim does embody a useful nugget of advice. Processing food in any way destroys some nutrients. The more you process the more nutrients you lose and it’s when you combine different processing techniques together that you find the real nutritional wasteland — that’s why highly-processed foods have such a poor reputation. Peeling isn’t too bad on its own, and cooking isn’t catastrophic, but combine the two and the results can be nutritionally devastating.
So as a rule of thumb peeling vegetables is a bad idea if you want them to retain their goodness. To the pedants though, once they peel away the layers of well-meaning misdirection, nutrition is more than skin deep.